The present invention relates to improvements in systems for treating a water mixture. In particular, it provides a system for pre-treating wastes from restaurants, food processing facilities and other industrial operations to reduce the concentration of the solids and oil/grease components which burden sewage processing facilities.
This waste generally includes various components derived in the cooking, processing and cleanup stages, mixed into a water vehicle. The components of this waste typically include meat and vegetable scraps, pieces of fat, melted fat, oil and the like. Bakery and food processing plant wastes generally include a variety of greases and oils, along with various solids components. Other industrial operations may include coarse solids and a free floating oil layer. Some of these solids and oil/greases can be successfully treated in conventional sewage treatment plants, but they require a long residence time in the sewage treatment facility and, therefore, are burdensome and expensive for sewage treatment purposes. This is true whether the solids are large pieces or comminuted in a garbage disposal.
Sewage treatment authorities have begun seeking ways to cope with the burdens placed on their capabilities by solids and oil/grease being discharged into the sewers. They have focused on commercial kitchen operations such as restaurants, cafeterias, hotels and motels, casinos, resort complexes, food-processing plants, airports and the like to attempt to decrease the amount of such materials received, or at least equitably spread the cost of treating sewage components. This has become particularly important in recent years as the funding to build additional sewage treatment plants has become scarce.
One of the schemes which sewage treatment authorities have used is to apply a surcharge to sewage treatment bills of commercial kitchen operations to reflect the added demands put upon the sewage treatment facility by sewage emanating from them. In other situations, treatment authorities have required that commercial kitchens simply stop discharging into the sewers, requiring the tanking of the discharge for other disposition. These requirements and their attendant added costs have imposed a burden upon commercial kitchens to deal with the effluent they generate.
It is known to pass the effluent through devices for removing melted oil and melted grease, to permit them to be recycled or otherwise removed from the effluent. Examples of these devices include the GRU grease recovery unit as described in U.S. Pat. Nos. 4,051,024 and 4,268,396 of Lowe Engineering Co., 2 Station Rd., Lincoln Park, N.J. 07035 and the BIG DIPPER Automatic Separating Apparatus as disclosed in U.S. Pat. No. 4,235,726 owned by Thermaco, Inc., assignee of the present application. As used herein, the term "oil/grease" means any material which in its liquid state is lighter than and immiscible in liquid water. Typical examples are the fats, greases and oils generated in kitchen operations, but other examples are lanolin, which may desirably be recovered from wool-treatment operations, and the oils used in machining operations, recovered from coolants used in such operations.
It is also known to use grease traps, particularly in-ground grease traps to separate floatable grease components from water, but these have been undesirable because they generate noxious odors and require periodic cleaning, a very unpleasant task. In addition, the costs associated with the disposal of the materials removed from these grease traps has soared as government regulations governing the disposal of these materials have been adopted.
Even with these operations, the effluent still has a high degree of biochemical oxygen demand because of the non-grease solids. A recent development by the assignee of the present application, Thermaco, Inc., and marketed under the name BIG FLIPPER has proven itself quite capable of moving solids from the effluent flow. The disclosure of U.S. patent application Ser. No. 07/557,962 filed Jul. 25, 1990 in the name of Batten and Miller covering such apparatus is incorporated by reference.
In addition, in some situations the solids and oil/grease have substantial value and it is desirable to recover these components. An example is the recovery of lanolin from wool processing operations.
However, the art still is without unitary, systemized means of automatically removing and recovering both oil/grease and solids from a water mixture to substantially reduce the burden on sewage treatment facilities in an easy-to-use, convenient, clean and sanitary fashion.